_Zapus hudsonius acadicus_ as here understood is a relatively wide-ranging subspecies. Populations at the southern periphery of its range are difficult to separate from populations at the northern periphery of the range of _Z. h. americanus_. These two geographic races represent opposite extremes of a clinal gradient and, as would be expected, geographic intermediates are morphologically similar. _Specimens examined._--Total, 156, distributed as follows: MAINE: _Aroostock County_: _Madawaska_, 6 (MCZ). _Hancock County_: _Mount Desert Island_, 9 (6 MCZ, 3 UM). _Piscataquis County_: _Mount Katahdin_, 1 (USNM); Sebec Lake, 4 (USBS); _Katahdin Lake_, 1 (USBS). _Sagadahoc Co._: Small Point Beach, 1 (Clev. MNH). _Somerset County_: east branch Penobscot River, 2 (USBS). _Washington County_: Columbia Falls, 1 (USBS). MASSACHUSETTS: _Essex County_: _Essex_, 4 (Clev. MNH); Wilmington, 4 (3 USBS, 1 USNM). _Worchester County_: _Lunenberg_, 2 (USBS); _1 mi. S Ayer_, 2 (MVZ); 2 mi. N Gilbertville, 1. NEW BRUNSWICK: _Charlotte County_: _6 mi. N St. Andrews_, 2 (NMC); 5 mi. N St. Andrews, 4 (NMC). _Carleton County_: _Debec_, 1 (MVZ). _Gloucester County_: Dalhousie, 2 (MVZ); _Miramichi Road, 15 mi. from Bathurst_, 4 (NMC); _Youghall_, 3 (NMC). _Madawaska County_: Baker Lake, 2 (NMC); _9 mi. NE Edmundston_, 4 (NMC); 5 mi. N St. Leonard, 5 (NMC). _Victoria Co._: _Tobique Point_, 1 (AMNH). _York County_: _Queensbury_, 1 (USBS). NEW HAMPSHIRE: _Carroll County_: _Intervale_, 1 (UM); _Ossipee_, 4 (3 USBS); _2 mi. S Ossipee_, 12 (2 USNM). _Coos County_: _Nathan Pond_, 1 (UM); Fabyans-Bretton Woods, Dartmouth Brook, 2 (UM); _Fabyans_, 1 (USNM); _3 mi. W Base Station_, 1; _Mt. Washington_, 1 (MVZ); _Pinkham Notch, 1900 ft._, 1 (USNM). _Grafton County_: _Franconia Notch, Profile Lake_, 1 (UM); Lebanon, 3 (UM). _Strafford Co._: _1 mi. E Durham_, 1 (UM). NEW YORK: _Essex Co._: Keene Valley, 5 (MCZ); _Keene Heights_, 5 (MCZ); _Minerva, 1700 ft._, 1 (AMNH). _Herkimer County_: Northwood, 7 (AMNH). _Rensselaer Co._: Berlin, 8 (AMNH). _Schenectady County_: _Glenville_, 1 (USBS). _Warren County_: _Lake George_, 5 (USBS). _Washington County_: _Patterns Mills_, 1 (USBS). NOVA SCOTIA: _Annapolis Co._: Bear River, 7 (NMC); _Lake Kedgemakooge_, 5 (UM); 2 mi. S Milford, 1 (AMNH). _Kings Co._: Black River Dist., 1 (NMC); _no exact locality_, 1 (NMC). _Shelburne County_: Doctors Cove, N Barrington Passage, 1 (NMC); _Barrington Passage_, 4 (NMC). PRINCE EDWARD ISLAND: no exact locality, 1 (USBS). QUEBEC: Ste. Anne des Monts, 1 (AMNH). VERMONT: _Addison County_: Orwell, 1 (MCZ); _Lamville County_: Mt. Mansfield, 2 (USBS). _Windham County_: _Whitingham_, 2 (AMNH).